1. Technical Field
The present disclosure relates to an automobile that is equipped with a three-phase motor and an inverter.
2. Description of Related Art
Conventionally, it has been proposed to learn an offset amount of a rotational position sensor that is attached to a rotor of a three-phase motor in the case where the three-phase motor is drivingly controlled based on a d-axis current and a q-axis current (e.g., see Japanese Patent Application Publication No. 2006-33993 (JP 2006-33993 A). The three-phase motor is drivingly controlled as follows. First of all, a d-axis current command and a q-axis current command are set based on a torque command of the three-phase motor. Subsequently, respective phase currents flowing through respective phases of the three-phase motor are detected by current sensors, and the respective phase currents are converted into a d-axis current and a q-axis current (three-to-two phase conversion) based on a rotational position of the three-phase motor from a rotational position sensor. Then, a d-axis voltage command and a q-axis voltage command are set based on the d-axis current command, the d-axis current, the q-axis current command and the q-axis current, and the d-axis voltage command and the q-axis voltage command are converted into respective phase voltage commands (two-to-three phase conversion) based on the rotational position of the three-phase motor from the rotational position sensor. Then, the three-phase motor is drivingly controlled by generating a PWM signal based on the respective phase voltage commands and performing switching control of an inverter. It should be noted herein that when the rotational position that is detected by the rotational position sensor includes an offset error, three-to-two phase conversion or two-to-three phase conversion is not adequately carried out, and a torque corresponding to a torque command cannot be output from the three-phase motor. Therefore, offset learning for learning an offset amount for subjecting the rotational position detected by the rotational position sensor to an offset correction is carried out. If the d-axis current command and the q-axis current command are made equal to 0 while the three-phase motor is in rotation, the d-axis voltage command is also equal to 0 in the case where the rotational position sensor does not include an offset error. However, in the case where the rotational position sensor includes an offset error, even when the d-axis current command and the q-axis current command are made equal to 0 while the three-phase motor is in rotation, the d-axis voltage command does not become equal to 0. Therefore, offset learning is carried out by adjusting the offset amount of the rotational position such that the d-axis voltage command becomes equal to 0 when the d-axis current command and the q-axis current command are made equal to 0.